Environmental Science
Chapter 4, section 4.1
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NOTES
Kinds of Ecosystems
Biomes of the World
 Earth is covered by hundreds of types of ecosystems which are grouped into a few biomes
 Biomes have distinctive climates, plants and organisms; they are named for their plant life but the main
determinant is the climate (temperature, precipitation, humidity, winds)
4.1 Forests Tropical Rainforests
 Occur in a belt around the Earth near the equator
 Always humid and warm; get about 250 cm (100 in) of rain per year
 Get strong sunlight year-round; maintains a climate with little seasonal variation in temperature.
 Ideal climate for growing plants; nourishes more plant species than any other biome (1 hectare
temperate forest contains 10 species of trees/ same area of tropical rainforest contain over 100 species)
 Soil is not rich, usually thin and poor; rapid decay of plants and animals return nutrients to soil---used up
by plants or washed away by rainfall
 Trees form aboveground roots—growing sideways from the trees, providing extra support
Rainforest: Plant Adaptations
 Plants grow in layers; trees more than 30 m (100 ft) tall form a dense canopy-absorbs at least 95% of the
sunlight
 Little light reaches below the canopy (understory); only trees and shrubs adapted to shade can grow (ex:
herbs with large flat leaves)
 When trees fall, tree seedlings adapted to grow quickly outcompete other seedlings
 Orchids and monkey ladder vines use the tall tree trunks for support high in the canopy
Rainforest: Plant Adaptations
 Plants grow in layers; trees more than 30 m (100 ft) tall form a dense canopy-absorbs at least 95% of the
sunlight
 Little light reaches below the canopy (understory); only trees and shrubs adapted to shade can grow (ex:
herbs with large flat leaves)
 When trees fall, tree seedlings adapted to grow quickly outcompete other seedlings
 Orchids and monkey ladder vines use the tall tree trunks for support high in the canopy
Rainforest: Animal Adaptations
 Incredible diversity of vegetation may have led to the evolution of the greatest diversity of animals
anywhere on Earth
 Little competition; most animals are specialists and are adapted for a specific purpose
 ex: antwrens – variety of species that eat insects at different layers; flowering plants that
can be pollinated by only one species of insect, bat or bird
 Some animals have developed elaborate methods for escaping predators; others have equally evolved
methods of capturing their prey
 ex: insects (butterfly) that looks like a leaf or twig; frogs that blend perfectly with
plants; poisons on their skin with bright colors to warn predators
Threats to Rainforests
 Used to cover 20% of Earth’s surface; today, only about 7%
 Every year tropical rainforests are stripped by logging operations or cleared for farming or cattle grazing
(the size of North and South Carolina combined)
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As they disappear, so do the habitats, plants and animals become extinct
Traditions and cultures are lost as native people are displaced
Help save the rainforests by looking for rain-forest friendly products and support organizations that
preserve tropical forests
Temperate Rain Forest
 Found in North and South America, Australia and New Zealand
 Pacific Northwest is home of the only North American temperate rainforest
 300 ft tall evergreen trees (Sitka spruce, Douglas fir) dominate the forest; mosses, lichens and ferns are
abundant
 Moisture pervades everything; cool, humid forest
 Located at 48° north latitude; rarely freezes (Pacific Ocean moderates the temperature)
Temperate Deciduous Forests
 Occur between 30° and 50° north latitude; seasonal variations can be extreme and growing season is
from 4 to 6 months
 Trees drop their leaves in the fall; summer temperatures can soar to 35° C ( 95° F); winter temperatures
plummet below freezing
 Deciduous forests are moist receiving 75-250 cm (30-100 in) of precipitation
 Rain and snow help decompose dead organic matter (leaves) contributing to the deep, rich soil
Deciduous Forests: Plant Adaptations
 Plants grow in layers; forest canopy is dominated by tall trees (maple, oak, birch)
 Small trees, shrubs, bushes grow in the understory
 Forest floor gets more light than the rain forest floor, thus more ferns, herbs and mosses grow there
 Plants are adapted to survive seasonal changes; seeds, bulbs and rhizomes become dormant in the
ground, trees lose their leaves
 In spring, as sunlight increases and temperatures increase, leaves re-emerge on trees, seeds germinate
and rhizomes and roots put forth new shoots
Deciduous Forests: Animal Adaptations
 Animals are adapted to forage the forest plants for food and shelter
 Squirrels eat nuts, seeds and fruits; bears eat leaves and berries, deer eat leaves from trees and shrubs;
birds nest in the tops of trees
 Birds are migratory—fly south in the winter to avoid the harsh weather; return in spring
 Animals that stay use various strategies for survival—bears and squirrels become inactive; insects enter
a state of very low metabolic activity
Taiga
 Aka: boreal forest; has rough terrain and the forest floor is sparsely vegetated
 Trees seem barren until you look up to see the green tops
 Located across the northern hemisphere just below the Arctic Circle; winters are 6 to 10 months and
extremely cold with subfreezing temperatures that plummet to -20°C (-4°F).
 The frost-free growing season may be as short as 50 days depending on the latitude; enhanced only by
constant daylight during the summer months
Taiga: Plant Adaptations
 Trees whose seeds develop cones (conifers, such as, pine, hemlock, fir, spruce) do not shed their needleshaped leaves; narrow shape leaves and waxy coating retain water when moisture in the ground in
frozen
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The shape (pointed) of the tree helps it shed snow; otherwise the snow would crush the tree
Conifer needles (contain acidic substances), acidify the soil when they fall, preventing other plants from
growing; blueberries, a few ferns and mosses can survive the acidic soil
Climate and acidity hinder decomposition which results in slow soil formation
Taiga: Animal Adaptations
 This biome is dotted with lakes and swamps in the summer, attracting birds that feed on insects, fish or
other wetland organisms
 Birds migrate south in the winter; shrews and voles burrow underground; moose and arctic hare eat
whatever vegetation they can find; lynx, wolves and foxes eat the hare and shed their brown summer fur
and re-grow a thick white fur in the winter